Buprenorphine (also known as (2S)-2-[(−)-(5R,6R,7R,14S)-9α-cyclo-propyl-methyl-4,5-epoxy-6,14-ethano-3-hydroxy-6-methoxymorphinan-7-yl]-3,3-di-methylbutan-2-ol and marketed under the trade names SUBUTEX® and SUBOXONE® (Indivior UK Limited) for relief of opioid addiction.
The chemical structure of buprenorphine is shown in Formula (1).

Buprenorphine is most often used to treat symptoms arising from opioid addiction and for the long term relief of pain. Currently, the commercial products are SUBUTEX® and SUBOXONE® marketed by RB Pharmaceuticals Limited (now Indivior). These products are in a tablet formulation and are intended to deliver therapeutic levels of buprenorphine for short periods of time of up to several hours and are typically taken either buccally or sublingually. However, the patient is required to supplement this dose at regular intervals, and there are often issues with diversion in patients with an opioid dependence problem. There is a need therefore for a longer term, non-divertible method of administering buprenorphine which delivers a constant and effective dose of the active to the patient over a period of up to 30 days, and which does not result in an unwanted accumulation of residual active in the patient's metabolism.
Various sustained release methods are employed in the pharmaceutical industry, for example, systems such as solid, biodegradable rods, or nondegradable reservoirs. These, however, typically require surgical implantation and furthermore, for the nondegradable delivery systems, a second surgical procedure is required to remove the empty reservoir.
There is a continuing need to develop products providing increased bioavailability of buprenorphine. In particular, there is a need to develop sustained release formulations of buprenorphine that do not suffer from low bioavailability, poor release kinetics, injection site toxicity, relatively large volume injections, and inconveniently short duration of release.